Controlled atmosphere system

ABSTRACT

A controlled atmosphere system comprising a plurality of open-ended chambers within an enclosure that may be refrigerated, each chamber provided with a detach-able closure either in the form of a flexible curtain or a solid lightweight partition wherein each chamber is supplied with its own controlled atmosphere.

This is a continuation-in-part of application Ser. No. 08/758,187, filedNov. 25, 1996

BACKGROUND OF THE INVENTION

It is well known to provide refrigeration and/or controlled atmospheresto maintain the freshness of perishable agricultural products, such asfruits, vegetables and flowers during storing or shipping of the same.In this connection, it is also well known that it is desirable to avoidfreezing the products to prevent damage and deterioration, and that alarge number of perishable products may be maintained in freshercondition at above-freezing refrigerated temperatures when they are alsomaintained in a low oxygen/high carbon dioxide content atmosphere, whichis known to be less conducive to rapid ripening and spoilage. Themaintenance of such a controlled atmosphere typically requires anair-tight seal of a refrigerated enclosure, which necessarily limitsaccess to the agricultural products during storage and transport. It isalso known to utilize a controlled atmosphere to store hardware such asguns or machinery.

BRIEF SUMMARY OF THE INVENTION

The essence of the present invention comprises the provision of amultiplicity of open-ended chambers within an enclosure which may or maynot be refrigerated, the chambers being of sufficient size toaccommodate one or more pallets bearing standard-sized containers suchas produce containers wherein each chamber is further provided withdetachable closure means capable of either covering the open end of thechamber or dividing the chamber into discrete zones or reducing the sizeof the chamber and with a means for gas circulation and appropriatehardware to receive and maintain a controlled atmosphere from acontrolled atmosphere supply. When used for the storage of produce, thechambers are preferably within a refrigerated enclosure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a perspective overview of the controlled atmosphere containersystem of the present invention, showing a plurality of individualopen-ended chambers within a refrigerated enclosure.

FIG. 2 is a side view of one of the open-ended chambers shown in FIG. 1.

FIG. 3 is a top view of one of the open-ended chambers.

FIG. 4 is a cross-sectional view of FIG. 3 taken along the plane 4--4.

FIG. 5 is a cross-sectional detailed view of that portion of FIG. 4designated as 5.

FIG. 6 is a cross-sectional view of element 18 of FIG. 5 taken along theplane 6--6.

FIG. 7 is an illustration of a portion of an exemplary combination gasmonitoring and control system.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, there is provided a controlledatmosphere container system comprising:

(a) a plurality of individual open-ended rigid chambers within anenclosure, each chamber being sized so as to accommodate at least onepallet having a standard-sized container thereon; and

(b) means to supply a controlled atmosphere to each chamber.

Each chamber is built of a rigid gas-impermeable material such as sheetmetal, fiberglass, thermosetting polymer or even wood with a sealantapplied thereto; in a preferred embodiment, the material is 14 ga.steel. To receive the controlled atmosphere and to maintain the same,each chamber is provided with removable or detachable closure means suchas a flexible curtain or a lightweight partition capable of covering theopen end of the chamber and reducing the effective size of the chamber,an inert gas inlet, a pressure relief valve, exhaust means, gascirculating means and gas composition testing means. Such an arrangementallows storage of a wide variety of agricultural and hardware productshaving different controlled atmosphere composition requirements forstorage and/or shipment, allows far more flexible access to the storeditems without concern for breaking the controlled atmosphere seal, andat the same time minimizes the volumetric flow requirements for thesupply and maintenance of a controlled atmosphere. In the case of storedproduce, a wide variety of produce having different controlledatmosphere requirements may be stored in the same refrigerated enclosurewhile permitting access to selected produce without risk of spoilage ofother stored produce.

In an especially preferred embodiment, the detachable closure means issubstantially gas-impermeable plastic sheeting, sail cloth-graderipstock nylon, treated canvas or a plexiglass sheet that may be sealedeither to the open end of the chamber or to the sides, top and bottom ofthe chamber at some point inward of the open end so as to reduce theeffective size of the chamber. The detachable closure is also preferablytransparent so as to allow observation of the condition of the producetherethrough, although non-transparent material such as plywood or evenlight gauge steel will function as well. The detachable closure may besupported by a lightweight rigid frame of, e.g., wood, PVC, ABS,aluminum, or other lightweight metal or alloy, or it may be unsupported.Because the detachable closure is not a permanent structure, the samemay simply be disposed of when it becomes worn or soiled.

To supply each chamber with a controlled atmosphere, each chamber isprovided with an inert gas inlet that is fed by a source of one or moreinert gases, the source preferably being valved. Typically, such inertgases include nitrogen, argon, carbon dioxide and ethylene, withnitrogen being used for flushing the chamber to rid it of atmosphericair and carbon dioxide, the latter being used in the case of producestorage to supply the bulk of the controlled atmosphere. The inert gasinlet may be as simple as a slit or hole in the detachable closure meansof sufficient size to receive a gas hose therethrough.

Flushing of the chamber takes place by securing the closure means tofour walls of the chamber at a predetermined point, preferably sealingthe same thereto by tape, opening the purge valve in the top of thechamber and flushing atmospheric air out with an inert gas such asnitrogen, then closing the purge valve and feeding the inert gas intothe chamber until the chamber contains the desired controlled atmospherecomposition, as indicated by gas composition testing means.

The chamber experiences variations in atmospheric pressure, whichvariations in turn produce fluctuations in the pressure of thecontrolled atmosphere within the chamber. These pressures areaccommodated by an exhaust valve provided in the upper portion of thechamber which, for economy of installation, is preferably a simplewater-filled trap that generally prevents the entry of atmospheric airinto the chamber, yet allows the escape of controlled atmosphere gasesupon a build-up in pressure of the same within the chamber.

To allow the perishable produce to be in contact with the controlledatmosphere, each chamber is provided with gas circulating means, whichis preferably a fan inside the chamber and duct work outside thechamber.

Each chamber is also preferably provided with humidification and/ordehumidification means so as to allow an increase or a reduction in thehumidity in the chamber, some of the humidity being caused byrespiration when produce is stored. The humidification/ dehumidificationmeans is preferably within the duct work outside the chamber, andincludes secondary gas circulation means such as a fan.

Each chamber is also preferably provided with a gas composition testerthat is in fluid communication with a gas composition monitor and infurther communication with a supply of inert gas, the arrangement actingin cooperation to allow precise monitoring and adjustment of thecontrolled atmosphere to suit the particular storage needs of theproduce in the chamber.

Turning now to the drawings, wherein like numerals refer to the sameelements, there is shown in FIG. 1 a perspective overview of thecontrolled atmosphere container system of the present invention, showinga plurality of individual open-ended chambers 10 within a refrigeratedenclosure 1, each chamber preferably being spaced apart from theadjacent chamber so as to permit circulation of refrigerated air betweenthe chambers. Each chamber 10 is sized so as to accommodate a singlelayer of a number of pallets having standard-sized containers such asproduce containers on the pallets, and also so as to accommodate astandard-sized lift truck of the type used in moving goods inwarehouses, or a manually operated pallet lift or a person. Preferably,the dimensions of each chamber are: from 5 to 8 feet in height;multiples of 48 inches in length; and multiples of 48-52 inches inwidth. When the system is used in a refrigerated enclosure 1, theenclosure may be of the type found in a warehouse, in a ship's cargohold, in a truck, in a rail car or in a modular cargo container.

Each chamber 10 is provided with detachable closure means 12 such as aflexible curtain or a lightweight partition, the closure means beingcapable of being detachably attached to the four walls of the chamber soas to substantially seal the same against the intrusion of atmosphericair. In a preferred embodiment, the removable closure means 12 istransparent or translucent flexible or rigid plastic or nylon sheetingthat is capable of being sealed to the chamber 10 simply by taping thesame to the four walls of the open chamber. In an especially preferredembodiment, the removable closure means 12 comprises substantiallygas-impermeable sail cloth-grade ripstock nylon mounted on a lightweightrigid frame. In the case of produce storage, transparency allows one toview the produce to ascertain whether any adverse conditions havedeveloped, such as an infestation of insects, undue respiration asindicated, for example, by the build-up of condensation on thedetachable closure 12, or spoilage. When the closure becomes undulysoiled or worn or torn, the same may simply be disposed of and replacedwith a fresh detachable closure.

In FIG. 2 there is shown a side view of one of the chambers 10,revealing an inert gas inlet 14, inert gas being supplied from an inertgas source such as a pressurized tank 15 and fed to inlet 14 via inertgas feed hose 15a. Alternatively, inert gas such as CO₂ may be suppliedby warming liquid CO₂ to a gaseous state, accumulating and temporarilystoring the gaseous CO₂ in a holding tank, then transforming apredetermined amount of the gaseous CO₂ to the chamber by an adjustable,timer-controlled valve. Such an automatic delivery system may be coupledwith an adjustable, timer-controlled evacuation pump to evacuate thechamber prior to charging it with CO₂, and to shut down the evacuationpump during the CO₂ -charging cycle. Such a system is described in U.S.Pat. No. 4,843,956, the details of which are incorporated herein. Theinert gas inlet may also be nothing more than a slit or a hole, sealablewith tape, in detachable closure 12, as shown in 12a of FIG. 4,sufficient in size to accommodate a gas hose from the inert gas supply.Typical inert gases used in the storage of agricultural produce such asfruit, nuts, vegetables and flowers include carbon dioxide, ethylene,nitrogen and argon, with carbon dioxide being the inert gas in mostwidespread use. Chamber 10 is provided with a purge valve 16 so as toallow flushing of atmospheric air from the chamber, valve 16 simplybeing opened when the chamber is being purged of atmospheric air andclosed when the chamber is substantially purged. Proper storage of mostagricultural produce calls for the presence of a minor amount of air, onthe order of 0.05 to 20 vol %. In order to achieve such a composition,atmospheric air may be allowed to reenter the chamber merely by openingpurge valve 16. Alternatively, pure oxygen from an oxygen source (notshown) may be supplied via gas inlet 14.

Because the interior of chamber 10 will experience fluctuations inpressure depending upon atmospheric pressure, each chamber is providedwith exhaust means 18 to allow the escape of gas upon a build-up ofpressure within the chamber. Preferably the exhaust means 18 is a simpletrap, best seen in FIGS. 5 and 6, the trap being filled with a liquidsuch as water to form a seal so as to both prevent the entry ofatmospheric air into chamber 10 and to prevent escape of the controlledatmosphere other than as is necessary to prevent an undue pressurereduction or build-up within the chamber.

As seen in FIG. 4, each chamber 10 is provided with gas circulatingmeans 20, which is preferably a blower of some sort such as a fan. Tofurther promote circulation of the controlled atmosphere within chamber10, each chamber may also be provided with ducting 21, shown in phantomin FIG. 4, to provide a pathway for the circulation of the controlledatmosphere from the top of the chamber to the chamber's bottom via ports21a and 2lb. In the event no ducting 21 is used, as would be the casewhen little circulation of the controlled atmosphere is needed, ports21a and 21b are closed to atmospheric air by the insertion of bungs (notshown). When ducting 21 is used, in order to prevent the build-up ofwater vapor, ducting 21 may be provided with dehumidification means 22,preferably comprising a desiccant bed. Alternatively, humidificationmeans (also designated 22) may be provided as necessary to maintain theproper level of humidity, the humidification means preferably comprisinga swap cooler or a mister. When a chamber is provided with eitherhumidification or dehumidification means 22, the chamber is alsopreferably provided with secondary gas circulating means 22a, such as afan.

In order to periodically test the composition of the controlledatmosphere within chamber 10, the chamber is preferably provided withgas composition testing means, comprising in combination a gascomposition sampler 24 connected to a gas analyzer 26 through samplerline 24a through valve 24b and gas analyzer line 24c. When a sample ofthe controlled atmosphere is desired to be taken and analyzed, valve 24bis opened, a vacuum is drawn by gas analyzer 26 upon line 24c and asample is thereby drawn into analyzer 26 and analyzed to ascertain itsprecise make-up. An especially preferred gas analyzer is onecommercially available from Pacific Ca Systems of Yakima, Wash. To theextent the controlled atmosphere requires more inert gas, the same maybe either manually or automatically supplied from pressurized tank 15.In the event that makeup gas is supplied automatically, gas analyzer 26is in electronic communication with a servovalve (not shown) by means ofa computerized controller (not shown) in inert gas supply line 15a,whereby the controller, in response to an electronic signal from the gasanalyzer that the concentration of inert gas in chamber 10 has fallenbelow a predetermined concentration, releases inert gas into thechamber. As seen in FIG. 7, each chamber 10 may be provided with its owngas composition testing means, with each sample line being in fluidcommunication with a common manifold feeding gas analyzer supply line24c.

The system of the present invention is useable for the storage andtransportation of all manner of goods, and is particularly well-suitedfor agricultural produce, including fruits, nuts, vegetables, mushroomsand flowers, and is capable of maintaining controlled atmospheres ofwidely varying compositions of from as little as 0.05 vol % oxygen to ashigh as 20 vol % and from as little as 0.04 vol % carbon dioxide to ashigh as 99.9 vol %. A good tabulation of the composition of controlledatmospheres for storage of various types of produce is found in"Proceedings of the Fourth National Controlled Atmosphere ResearchConference," Jul. 23-26, 1985, North Carolina State University, Raleigh,N.C. In addition, the system of the present invention is capable ofmaintaining multi-component controlled atmospheres, simply by theaddition of multiple inert gas inlet ports.

EXAMPLE

Freshly harvested blueberries containing about 1% unripe green berriesand red berries were cleaned, sorted, graded and packaged the same dayinto 6 oz. hallocks placed in crates which were then loaded onto 6standard-sized pallets, each measuring 40×wide×48" long×72" in height.Each pallet was then precooled to 32° F. and placed into a controlledatmosphere chamber fabricated from 14 ga. steel and having substantiallythe same design shown in FIGS. 2-4, with six pallets to each chamber.The chambers were within a refrigerated warehouse enclosure maintainedat 32° F.

The open end of each chamber was sealed with 6 -mil-thick clearpolyethylene taped to the four walls of the chamber. Purge valve 16 wasopened, and atmospheric air was flushed with nitrogen until the oxygenlevel reached 8 vol %. Carbon dioxide was then supplied via inert gasinlet 14 until its concentration reach 12 vol %. The carbon dioxide alsoreduced the oxygen concentration to 6 vol %. Interior fan 20 was turnedon for slight gas circulation within the chamber. The temperature in thechambers stayed at 33-34° F.

The blueberries were so stored for a total of 45 days, with theatmosphere being monitored daily by analyzer 26. The fruit wasreinspected upon opening the chambers and actually improved in overallgrade due not only to the total absence of decay, mold, mildew andinsect damage, but also to the ripening of 75% of the green and redberries.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention in the use of such terms andexpressions of excluding equivalents of the features shown and describedor portions thereof, it being recognized that the scope of the inventionis defined and limited only by the claims which follow.

I claim:
 1. A controlled atmosphere container system comprising:(a) anenclosure; (b) a plurality of individual open-ended rigid chamberswithin said enclosure, each chamber being sized so as to accommodate atleast one pallet bearing a standard sized container wherein each chamberis further provided with(i) substantially gas-impermeable detachableclosure means capable of closing the open end of said chamber andvarying the size of said chamber, (ii) an inert gas inlet, (iii) apressure relief valve, (iv) exhaust trap, (v) gas circulating means, and(vi) gas composition testing means; and (c) atmosphere control means tosupply a controlled atmosphere to each chamber wherein said detachableclosure means comprises a fabric supported by a lightweight frame. 2.The system of claim 1 wherein said fabric of said detachable closuremeans is ripstock nylon.
 3. The system of claim 1 wherein said gascirculating means is a fan with associated ducting capable ofcirculating gases within said chamber.
 4. The system of claim 1including secondary gas circulating means and dehumidification means. 5.The system of claim 1 including secondary gas circulating means andhumidification means.
 6. The system of claim 1 wherein said inert gas isCO₂ and said atmosphere control means comprises a liquid CO₂ containercontaining liquid CO₂, a heater for converting said liquid CO₂ togaseous CO₂, a storage vessel for accumulating and temporarily storingsaid gaseous CO₂, a adjustable, timer-controlled valve in fluidcommunication with said storage vessel and said chamber for charging apredetermined amount of said gaseous CO₂ to said chamber, an adjustable,timer-controlled evacuation pump for evacuating said chamber prior tocharging the same with said gaseous CO₂, and electrical switching toprevent operation of said evacuation pump while said chamber is beingcharged.
 7. The system of claims 1, 2 or 6 within a refrigeratedenclosure.
 8. A controlled atmosphere container system comprising:(a) arefrigerated enclosure; (b) a plurality of individual open-ended andfree-standing chambers within said refrigerated enclosure, wherein eachchamber is provided with(i) substantially gas-impermeable detachableclosure means capable of closing the open end of said chamber andvarying the size of said chamber, (ii) an inert gas inlet, (iii) apressure relief valve, (iv) exhaust trap, (v) gas circulating means, and(vi) gas composition testing means; and (c) atmosphere control means tosupply a controlled atmosphere to each chamber wherein said detachableclosure means is selected from the group consisting of a flexiblecurtain and a lightweight partition.
 9. The system of claim 8 whereinsaid detachable closure means is plastic sheeting.
 10. The system ofclaim 8 wherein said detachable closure means is treated canvas.
 11. Thesystem of claim 8 wherein said detachable closure means is selected fromthe group consisting of plexiglass, plywood and light gauge steel.